<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <video id="video_demo" width="300" height="250" controls="">
        <!-- //它会寻找能播放的第一个资源 -->
        <source src="http://pwoj2h129.bkt.clouddn.com/FP16nFesK-VQ_2RQBYvF1.mp4" type="audio/mkv"></source>
        <!-- <source src="../../../../../../视频/simplescreenrecorder-2019-07-04_08.13.43.mkv" type="audio/mkv"></source> -->
        <!-- 您的浏览器不支持 HTML5 video 标签。 -->
    </video>

    <br />

    <div style="text-align: center">
        <button onclick="playpause()">暂停/播放</button>
        <button onclick="makeBig()">放大</button>
        <button onclick="makeSmall()">缩小</button>
        <button onclick="makeNormal()">普通</button>
    </div>
    <script>
        var _video = document.getElementById("video_demo");

        //播放或暂停
        function playpause() {
            if(_video.paused) {
                _video.play();
            } else {
                _video.pause();
            }
        }

        //放大
        function makeBig() {
            _video.width = 500;
            _video.height = 400;
        }

        //缩小
        function makeSmall() {
            _video.width = 200;
            _video.height = 100;
        }

        //普通
        function makeNormal() {
            _video.width = 300;
            _video.height = 250;
        }
    </script>
</body>
</html>